Patent GB-630698-A (GB)
Title: Improvements in or relating to means for identifying areas or lines in a radio navigational system
IPC: G01S19/25
Filed: 1946-11-06
Abstract: 630,698. Automatic phase control systems. DECCA RECORD CO., Ltd. Nov. 6, 1946, No. 33035. Convention date, June 3. [Class 38 (iv)] [Also in Group XL (c)] Lane identification in the radio frequency navigation system described in Specification 620,479 is provided by periodically arresting radiation from one of the stations and simultaneously radiating from one of the other two stations a first pair of signals of two of the harmonicallyrelated frequencies used in the normal system and from the third station a second pair of signals of frequencies, one equal to the third normal transmission frequency and the other a fourth frequency being a harmonic of the same fundamental of the other three and in fixed phase relationship therewith. This produces a lane identification pattern of coarser form and uses only one radio frequency more than the number used in the original system. The transmissions may be made according to the following schedule, it being assumed that normal transmission consists of the radiation of signals of 60, 80 and 90 Kc. respectively, with a fixed multiple phase relation from spaced stations A, B and C : First. Normal transmission. Second. A : 60 and 70 Kc. signals ; B : off ; C : 90 and 80 Kc. signals. Third. A : 60 and 70 Kc. signals ; B : 80 and 90 Kc. signals ; C : off. Fourth. Normal transmission. Only one additional frequency, 70 Kc. is used and by comparing the beat frequency of the 60 and 70 Kc. signals with that of the 80 and 90 Kc. signals in the second mode of operation one lane in 18 of the A.C. pattern, and in the third mode of operation one lane in 24 of the A, B pattern, can be determined. The transmitters. At the master station A, Fig. 3, a generator 36, generating harmonics of the common factor frequency 10 Kc. of the system feeds amplifier 31 tuned to accept and amplify the 60 Kc. harmonic and feed it to antenna 33. The 70 Kc. harmonic is selected in unit 37 and fed through mechanical phase adjuster. 38, electrical phase adjuster 39, and amplifier 32 also to feed antenna 33. During normal transmission switch 53 is open and no 70 Kc. signals are radiated, during lane identification however, switch 53 is closed preferably by an automatic time control device. A pickup loop 40 picks up the 70 and 80 Kc. signals radiated and feeds them, through separate frequency multiplying channels bringing them to the same frequency, to a phase discriminator 46 with an indicator 50 and a control voltage output which is applied to phase adjuster 39 in such a way as to maintain the multiple phase relationship between the 60 and 70 Kc. signals constant. At the slave transmitter B 60 and 70 Kc. signals are received from A on a loop 59 and the 60 Kc. continuous signals fed to frequency dividing and multiplying chains culminating in 80 Kc. amplifier 54 and 90 Kc. amplifier 55 both feeding antenna 56. Correct phase adjustment of the dividers of the chain is maintained by synchronizing them with the 70 Kc. signals amplified and adjusted in phase units 94 and 95. The signals radiated are picked up on loop 77 and for the purpose of synchronizing the phase of the 80 Kc. signal with the 60 Kc. signal from the master station the received 80 Kc. signals from loop 77 are applied through tuned amplifier 79 and frequency trebler 80 to one input of phase discriminator 75. The other input of the discriminator is fed with the 60 Kc. received signals from loop 59 multiplied four times in frequency at 73. The output voltage of the discriminator is applied to an electronic phase adjuster 62 in the 80 Kc. energization channel in such a way as to maintain the multiple phase relationship of the 80 Kc. and 60 Kc. signals constant. During transmission of the 90 Kc. signals these are synchronized by obtaining the 10 Kc. beat frequency of the 80 and 90 Kc. signals received on loop 77 by detector 88 and feeding them to discriminator 87 ; the other input of the discriminator being fed with the beat frequency of the 60 and 70 Kc. signals received on loop 59, from detector 84 and the output being applied to phase adjuster 67 in the 90 Kc. energization channel. Switch 96 is operated in timed sequence and in synchronism with switch 53 at the main transmitter to give the required operating sequence. The C slave transmitter is similar to the B transmitter but the 80 and 90 Kc. control and switching arrangements are interchanged. For more ambiguous lane identification system 60 Kc. and 80 Kc. may be radiated from the master station and 70 Kc. and 90 Kc. from each of the slave stations in turn ; the comparison at the receiver being between the 20 Kc. beat frequencies signals. The method of setting up the system to give a determined pattern is described in the Specification and harmonic generators, included in the equipment, may be switched in to check if there has been any phase shift. Specifications 620,480, 620,507, [both in Group XXXVI], 625,983, [Group XL (c)], and 628,747 are referred to.